Yup. That was it. I'm afraid this auto home story thing has made me a little paranoid.
Looking at this, I've found that ALT+SHIFT is a quick and easy way to offset the edit plane.
Many thanks.
David Collins
Win10 64bit Intel i7 6700 3.40 Ghz, 32 Gb RAM, GeForce RTX 3070
AC 27.0 (4001 INT FULL)